1. Field of the Invention
The invention relates to a film stretcher that stretches a film material having a film-like shape, sheet-like shape, or the like.
2. Description of the Related Art
Japanese Patent Application Publication No. 2004-67804 (JP-A-2004-67804) describes a film stretcher (tenter type). The film stretcher includes chains having a large number of holding means, such as clips, on both sides of a film. Both ends of the film are held by the clips provided for the chains. The chains on both sides of the film are driven along respective guide rails, that is, in a direction to widen the film in the width direction. In this manner, the film stretcher stretches the film.
However, in the above film stretcher, the film is stretched in such a manner that both ends of the film are held by the clips that are located at intervals in the direction in which the film is driven (transported). Thus, stretching stress concentrates on portions near the clips. For this reason, the film is stretched ununiformly at portions near the clips, and, by extension, perforation is formed in the film. This causes a neck-in (contraction in the film width direction) between the adjacent clips. Hence, it is considerably difficult to reduce the thickness of the film.